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Abstract Thermally activated annealing in semiconductors faces inherent limitations, such as dopant diffusion. Here, a nonthermal pathway is demonstrated for a complete structural restoration in predamaged germanium via ionization‐induced recovery. By combining experiments and modeling, this study reveals that the energy transfer of only 2.4 keV nm⁻¹from incident ions to target electrons can effectively annihilate pre‐existing defects and restore the original crystalline structure at room temperature. Moreover, it is revealed that the irradiation‐induced crystalline‐to‐amorphous (c/a) transformation in Ge is reversible, a phenomenon previously considered unattainable without additional thermal energy imposed during irradiation. For partially damaged Ge, the overall damage fraction decreases exponentially with increasing fluence. Surprisingly, the recovery process in preamorphized Ge starts with defect recovery outside the amorphous layer and a shrinkage of the amorphous thickness. After this initial stage, the remaining damage decreases slowly with increasing fluence, but full restoration of the pristine state is not achieved. These differences in recovery are interpreted in the framework of structural differences in the initial defective layers that affect recovery kinetics. This study provides new insights on reversing the c/a transformation in Ge using highly‐ionizing irradiation and has broad implications across materials science, radiation damage mitigation, and fabrication of Ge‐based devices. 

Abstract The temperature dependence of amorphization in a high-entropy pyrochlore, (Yb_0.2Tm_0.2Lu_0.2Ho_0.2Er_0.2)₂Ti₂O₇, under irradiation with 600 keV Xe ions has been studied using in situ transmission electron microscopy (TEM). The critical amorphization dose increases with temperature, and the critical temperature for amorphization is 800 K. At room temperature, the critical amorphization dose is larger than that previously determined for this pyrochlore under bulk-like 4 MeV Au ion irradiation but is similar to the critical doses determined in two other high-entropy titanate pyrochlores under 800 keV Kr ion irradiation using in situ TEM, which is consistent with reported behavior in simple rare-earth titanate pyrochlores. Graphical abstract 

Abstract Compositionally complex materials have demonstrated extraordinary promise for structural robustness in extreme environments. Of these, the most commonly thought of are high entropy alloys, where chemical complexity grants uncommon combinations of hardness, ductility, and thermal resilience. In contrast to these metal–metal bonded systems, the addition of ionic and covalent bonding has led to the discovery of high entropy ceramics (HECs). These materials also possess outstanding structural, thermal, and chemical robustness but with a far greater variety of functional properties which enable access to continuously controllable magnetic, electronic, and optical phenomena. In this experimentally focused perspective, we outline the potential for HECs in functional applications under extreme environments, where intrinsic stability may provide a new path toward inherently hardened device design. Current works on high entropy carbides, actinide bearing ceramics, and high entropy oxides are reviewed in the areas of radiation, high temperature, and corrosion tolerance where the role of local disorder is shown to create pathways toward self-healing and structural robustness. In this context, new strategies for creating future electronic, magnetic, and optical devices to be operated in harsh environments are outlined. 

Abstract Effects of electronic to nuclear energy losses (S_e/S_n) ratio on damage evolution in defective KTaO₃have been investigated by irradiating pre-damaged single crystal KTaO₃with intermediate energy O ions (6 MeV, 8 MeV and 12 MeV) at 300 K. By exploring these processes in pre-damaged KTaO₃containing a fractional disorder level of 0.35, the results demonstrate the occurrence of a precursory stage of damage production before the onset of damage annealing process in defective KTaO₃that decreases with O ion energy. The observed ionization-induced annealing process by ion channeling analysis has been further mirrored by high resolution transmission electron microscopy analysis. In addition, the reduction of disorder level is accompanied by the broadening of the disorder profiles to greater depth with increasing ion fluence, and enhanced migration is observed with decreasing O ion energy. SinceS_e(∼3.0 keV nm⁻¹) is nearly constant for all 3 ion energies across the pre-damaged depth, the difference in behavior is due to the so-called ‘velocity effect’: the lower ion velocity below the Bragg peak yields a confined spread of the electron cascade and hence an increased energy deposition density. The inelastic thermal spike calculation has further confirmed the existence of a velocity effect, not previously reported in KTaO₃or very scarcely reported in other materials for which the existence of ionization-induced annealing has been reported. In other words, understanding of ionization-induced annealing has been advanced by pointing out that ion velocity effect governs the healing of pre-existing defects, which may have significant implication for the creation of new functionalities in KTaO₃through atomic-level control of microstructural modifications, but may not be limited to KTaO₃. 

The ionoluminescence of strontium titanate (SrTiO3) under the intense electronic excitation produced by 3 MeV H, 19 MeV Si, and 19 MeV Cl ions was investigated for temperatures between 30 and 100 K. In addition to previously reported emission bands centered at 2.0 eV, 2.5 eV, and 2.8 eV, an asymmetric, narrow emission band centered at 3.15 eV was observed for the first time under ion irradiation. The 3.15 eV band appeared only under heavy ion irradiation (19 MeV Si and Cl) and at temperatures below ~70 K. The absence of the 3.15 eV emission under proton irradiation indicates that impurities and the pre-irradiation defect population likely play little or no role in the emission process, while electronic excitation density does. At the same time, the absence of fluence-dependent growth in the yield suggests that irradiation-induced defects are also unlikely to be the main cause of the emission. Upon comparing the proton induced ionoluminescence, heavy ion induced ionoluminescence, and available literature on low temperature photoluminescence of strontium titanate, a self-consistent interpretation emerges, where the 3.15 eV emission is associated with the recombination of large polarons. 

It is widely accepted that the interaction of swift heavy ions with many complex oxides is predominantly governed by the electronic energy loss that gives rise to nanoscale amorphous ion tracks along the penetration direction. 

The high-entropy concept was applied to synthesize a set of rare-earth perovskites REBO3 (RE = La, Pr, Nd, Sm, Eu, Gd) with the B-site occupied by Sc, Al, Cr, Ni, and Fe in equimolar ratios. All samples crystallize in the orthorhombic Pnma space group. Using an extended set of characterization measurements, the effects of multi-component material design and rare-earth selection on the electronic properties are explored. Transport measurements show semiconducting behavior. PrBO3, SmBO3, and LaBO3 show low-temperature magnetic ordering, with the ordering temperature shifting with the moment on the A-site.